Three-dimensional display systems are well known and fall into several technical categories. Stereoscopic systems rely on presenting two different images to the two eyes of a viewer. This may be achieved by projecting two images onto the same screen, and providing a viewer with polarized glasses or glasses with coloured filters so that a first image is seen only by the viewer's right eye, and a second image is seen only by the viewer's left eye. Autostereoscopic systems, which do not require glasses, are also available and present separate images to each eye via a parallax barrier or lenticular array.
In stereoscopic systems, the images which are presented to the left and right eyes of the viewer are the same images, whatever the position of the viewer with respect to the image. The viewer cannot therefore see around the sides or back of the image, but is simply presented with a single perspective view, with the illusion of depth. Eye tracking devices have been used to follow the gaze of a viewer, and adjust the image in real time. However, such systems are suitable only for viewing by a single viewer.
Volumetric displays are also known, and include ‘swept-volume’ devices. Such displays rapidly project slices of a three dimensional image onto a moving two dimensional surface, relying on persistence of vision in order to present a three dimensional image to a viewer. However, since the display volume in such devices must include a rapidly moving mechanical part, use of a swept-volume display as an interactive device is impossible, since the image cannot be touched without causing injury. These displays are also unsuitable for use in mobile devices such as laptops, tablets and phones.
‘Static-volume’ devices are also known, and avoid the need for moving parts in the display volume. An example static-volume display device focuses a laser on a point in air, where it ionises the air at that point, creating a ball of plasma. Such displays do not require moving parts in the display volume, but the displayed image is made up of relatively large pixels, so the display resolution is low. The display is also limited to a single colour, or small number of colours.
Three-dimensional images can also be produced by holography. However, known holographic displays do not offer user interaction.
Many of the above mentioned existing types of three-dimensional display produce a virtual image, or an image which is confined within the display. A virtual, as opposed to real, image cannot be touched and therefore cannot offer user interaction.
It is an object of this invention to provide a three-dimensional interactive display which reduces or substantially obviates the above mentioned problems.